The Retroviral Diseases Section of the HIV and AIDS Malignancy Branch conducts translational clinical and laboratory research aimed at the development of novel therapies for HIV infection and AIDS- related malignancies. It also conducts laboratory research focused on an understanding of these diseases. During the past year, the group has investigated the role of a conserved cysteine at position 95 on the activity of HIV protease. We have previously found that glutathiolation of Cys 95 (in the dimer interface) abolishes HIV-1 protease activity. HIV virions with mutations of Cys 95 have been generated and we are studying the effects that these mutations have on the fitness of HIV under varying conditions. We have recently found that nearly all retroviral proteases are regulated by oxidizable amino acids at the dimer interface and that in the case of HIV-1, this occurs by interfering with dimer formation. HIV from some patients who have developed resistance to protease inhibitors have been also found to develop a mutation in Cys95, and we are trying to understand the evolutionary pressures leading to this mutation. This work on HIV protease has identified the dimer interface as a potential therapeutic target, and we are attempting to design inhibitors of HIV protease that act as this site. We are also investigating the role of Kaposi's sarcoma-associated herpes virus (KSHV), also called human herpesvirus-8 (HHV-8), in the pathogenesis of Kaposi's sarcoma (KS). We have found that hypoxia can activate latent KSHV to undergo lytic replication. We have found evidence that several genes of KSHV are specifically upregulated by hypoxia. Two of these genes are Rta and viral Bcl-2. We had previously found that a gene of unknown function, ORF34, is specifically activated by hypoxia. ORF34 is part of a cluster of genes (ORF34 to 37), and we are currently analyzing the structure of this cluster cluster and their regulation by hypoxia. One of these genes, ORF36, can phosphorylate ganciclovir, and activation of this gene by hypoxia may be able to be used to therapeutic benefit in KSHV-associated tumors, especially PEL. As an outgrowth of the work on hypoxia and its effects on KSHV, we have also explored the differential activity of hypoxia inducible factors (HIF) 1 (HIF-1) and 2 (HIF-2) on the activation of cellular genes, and have identified a number of genes that are selectively activated by either HIF-1 or HIF-2. We are also conducting several clinical trials to evaluate novel therapies for Kaposi's sarcoma with a focus on anti-angiogenesis approaches. We have found that the cytokine IL-12 has long-acting activity in Kaposi's sarcoma have also conducted a trial to study the combination of IL-12 and a liposomal anthracycline in patients with advanced KS. We are also studying antibody to VEGF as a therapeutic agent in KS. We have initiated trials to study the natural history study of multicentric Castleman's disease (MCD), which is also caused by KSHV and plan to explore a therapeutic strategy involving antiviral drugs activated by KSHV. We have also recently initiated a trial studying novel approaches involving KSHV gene activation and then cytotoxic chemotherapy in primary effusion lymphoma (PEL). We are also studying infusional chemotherapy as therapy for AIDS-associated lymphoma in collaboration with the Experimental Immunology and Transplantation Branch. In regard to anti-HIV therapy, we are initiating a clinical trial to explore whether specific immunity can be developed to a crucial sequence in reverse transcriptase.